1. Field of the Invention
This invention relates to printed wiring boards and, more specifically, to a system for enhancing the current carrying capacity of such boards.
2. Brief Description of the Prior Art
There is a present need for high current carrying capacity printed wiring boards in conjunction with electronic applications to automotive drive motors. In such applications, high current relays are soldered to the densely packed mixed technology circuit board and are expected to carry 30 amperes DC current without insulated wiring connecting the relay and the connector. The cost for such circuitry in such applications has been prohibitive in conjunction with known prior art techniques.
On the other hand, presently known Surface Mount Technology (SMT) has caused an increase in the packing density of SMT circuitry boards. This increased density has limited the current carrying capacity of SMT printed wiring boards (PWBs) due to the need for fine line and space circuitry (0.010.times.0.010 or less). In the prior art, current carrying capacity was increased by using 2 to 4 mil copper foil in PWBs. It is well known in the PMB fabrication art that fine line circuit boards cannot be produced out of heavy copper foil due to excessive undercutting of the traces caused by long copper etching cycles. With these constraints, the current carrying capacity of tightly packed pin-in-hole or surface mount assemblies has suffered. It is therefore apparent that a need has arisen for high current carrying capacity printed wiring boards which can be produced economically.